Semicircular lipoatrophy is a new entity with horizontal depressions involving half the circumference of thigh, on the antero-lateral aspect. After seven female patients we observed this condition for the first time in the male. Therefore semicircular lipoatrophy is not specific to the female. The cause could not be determined clinically, nor by biochemical, immunological or histological methods. In our opinion semicircular lipoatrophy represents an ischemic atrophy of the fatty tissue, manifested by repeated microtraumata (corners of wash-basins, dressing tables or desks). The perfusion on the antero-lateral aspect of the thighs is tenous, especially when the course of the lateral femoral circumflex artery varies from the normal. In this case semicircular anastomotic areas become ischemic and horizontal bands of lipoatrophy result.